using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using FinlyticCore.Dtos.Settings;
using FinlyticCore.Models.Settings;
using FinlyticCore.Services;

namespace FinlyticEngine.Tests.TestSupport;

/// <summary>
/// Hand-written in-memory fake for <see cref="ISettingsService"/>. Rules.md §13 forbids test mocks inside
/// production assemblies, so this fake lives exclusively in the test project. Only the
/// <see cref="SettingKey{T}"/> overloads are exercised by the services under test
/// (CompositeOpportunityScorer, TradeLifecycleService); the remaining interface members throw
/// <see cref="NotSupportedException"/> so an accidental new dependency on them fails loudly instead of
/// silently returning a wrong default.
/// </summary>
public class FakeSettingsService : ISettingsService
{
    private readonly ConcurrentDictionary<string, object?> _overrides = new(StringComparer.Ordinal);

    /// <summary>
    /// Registers an explicit value for the given setting key, overriding its compiled-in default for the
    /// lifetime of this fake instance.
    /// </summary>
    public void Set<T>(SettingKey<T> key, T value) => _overrides[key.Name] = value;

    /// <inheritdoc />
    public Task<T> GetSettingAsync<T>(SettingKey<T> key, CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(key);
        if (_overrides.TryGetValue(key.Name, out var value) && value is T typed)
        {
            return Task.FromResult(typed);
        }

        return Task.FromResult(key.DefaultValue);
    }

    /// <inheritdoc />
    public Task SetSettingAsync<T>(SettingKey<T> key, T value, CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(key);
        _overrides[key.Name] = value;
        return Task.CompletedTask;
    }

    /// <inheritdoc />
    public Task<T> GetSettingAsync<TEnum, T>(TEnum enumKey, T defaultValue = default!, CancellationToken cancellationToken = default)
        where TEnum : struct, Enum
        => throw new NotSupportedException("Not exercised by any service under test in this suite.");

    /// <inheritdoc />
    public Task SetSettingAsync<TEnum, T>(TEnum enumKey, T value, CancellationToken cancellationToken = default)
        where TEnum : struct, Enum
        => throw new NotSupportedException("Not exercised by any service under test in this suite.");

    /// <inheritdoc />
    public Task<T> GetSettingAsync<T>(string key, T defaultValue = default!, CancellationToken cancellationToken = default)
        => throw new NotSupportedException("Not exercised by any service under test in this suite.");

    /// <inheritdoc />
    public Task SetSettingAsync<T>(string key, T value, CancellationToken cancellationToken = default)
        => throw new NotSupportedException("Not exercised by any service under test in this suite.");

    /// <inheritdoc />
    public Task<List<DynamicSettingDto>> GetAllRegisteredSettingsAsync(IEnumerable<Type>? customKeyHolders = null, CancellationToken cancellationToken = default)
        => throw new NotSupportedException("Not exercised by any service under test in this suite.");

    /// <inheritdoc />
    public Task UpdateSettingsAsync(Dictionary<string, object?> updatedSettings, CancellationToken cancellationToken = default)
        => throw new NotSupportedException("Not exercised by any service under test in this suite.");
}